Non-Fermi Liquid Behavior Close to a Quantum Critical Point in a Ferromagnetic State without Local Moments

TL;DR

This study reveals non-Fermi liquid behavior near a quantum critical point in a weak itinerant ferromagnet without local moments, showing critical scaling and strong spin fluctuations linked to reduced dimensionality.

Contribution

It demonstrates NFL behavior and critical scaling in a system without local moments, expanding understanding of quantum criticality in itinerant ferromagnets.

Findings

Logarithmic divergence of specific heat in both ferromagnetic and paramagnetic states.

Critical exponents show weak composition dependence near QCP.

Large paramagnetic moment nearly independent of doping.

Abstract

A quantum critical point (QCP) occurs upon chemical doping of the weak itinerant ferromagnet Sc_{3.1}In. Remarkable for a system with no local moments, the QCP is accompanied by non-Fermi liquid (NFL) behavior, manifested in the logarithmic divergence of the specific heat both in the ferro- and the paramagnetic states. Sc_{3.1}In displays critical scaling and NFL behavior in the ferromagnetic state, akin to what had been observed only in f-electron, local moment systems. With doping, critical scaling is observed close to the QCP, as the critical exponents, and delta, gamma and beta have weak composition dependence, with delta nearly twice, and beta almost half of their respective mean-field values. The unusually large paramagnetic moment mu_PM~1.3 mu_B/F.U. is nearly composition-independent. Evidence for strong spin fluctuations, accompanying the QCP at x_c = 0.035 +- 0.005, may be ascribed to the reduced dimensionality of Sc_{3.1}In, associated with the nearly one-dimensional Sc-In chains.